Fixing some errors in sub-document example

Typo and stuff

Since this function returns a DWORD (32-bit) on Windows, the upper
and lower shorts are xor'd together.

Adding bson_malloc to the list of exported symbols

On some versions of solaris, braces are required around the PTHREAD_ONCE_INIT
macro. But apparently not all versions. How fun!

didn't appropriately handle the deprecated binary format (in particular
the redundant int32).  Fixing that up

bson_iter_binary and bson_append_binary don't appropriately write or
read BSON_SUBTYPE_BINARY_DEPRECATED.  These tests test for that
functionality.

Specifically we don't add or handle the redundant leading int32 payload

also check for posix_memalign() and memalign().